Wireless Ad Hoc and Sensor Networks

Admission Controller Design for High-Speed Networks 153If the traffic is estimated accurately, then the traffic flow modeling errorcan be made very small, which results in a small estimation error in bufferoccupancy. By minimizing the buffer occupancy estimation error, it isshown that the accumulated traffic at the switch is estimated accurately.In high-speed networks, each source should be able to use the availablebandwidth up to its peak bit/cell rate (PBR/PCR). The goal of a bandwidthestimation and allocation scheme, then, is to enable the availablebandwidth to be fully utilized while maintaining a good QoS, where theQoS parameters are the packet or cell loss ratio (PLR/CLR), and transferdelay. In this chapter, the objective of selecting a suitable traffic estimationscheme is to estimate the current bandwidth usage, predict the futurebandwidth requirement, and to identify the available capacity for newsources in the next measurement interval.Equation 4.5 calculates the packet/cell losses encountered at the switchfabric because of the traffic estimation scheme. In this chapter, it is envisionedthat by appropriately using an adaptive estimator in discrete timeto provide the traffic estimate, f ˆ( x( k)), the error in buffer length, and hencethe packet/cell losses, can be minimized. The actual packet/cell lossesare related to the bandwidth requirement for the next measurement interval.By appropriately combining the bandwidth estimated using the predictedtraffic conditions, packet/cell losses, along with the queued data at theswitch, one can estimate the bandwidth required to satisfy the target QoSin the next measurement interval.The buffer occupancy estimation error system expressed in Equation4.5 is used to focus on selecting discrete-time parameter-tuning algorithmsthat guarantee the QoS by appropriately assigning the adequate bandwidthto the existing sources, provided no congestion exists. The proposedadaptive methodology can be best described as follows: The adaptivescheme at the ingress node/switch fabric estimates the network traffic;this estimated traffic, packet/cell losses, and target transfer delay are usedto compute the equivalent bandwidth required to meet the target QoS.4.3 Adaptive Traffic Estimator DesignIn the two-layer NN case, the tunable weights enter in a nonlinear fashion.Stability analysis by Lyapunov’s direct method is performed using novelweight-tuning algorithms that are developed in this chapter. Assume, therefore,that there exist some constant ideal weights W and V for a two-layerNN so that the nonlinear traffic accumulation function can be written asT Tf( x( k)) = W ϕ ( V ϕ ( x( k))) + ε( k)2 1(4.6)